Fix identity and user retrieval when special characters are used

app/models/identity.rb

@@ -12,6 +12,7 @@
 class Identity < ActiveRecord::Base
   include Sortable
+  include CaseSensitivity
   belongs_to :user
   validates :provider, presence: true

lib/gitlab/ldap/user.rb

@@ -14,7 +14,7 @@ module Gitlab
           # LDAP distinguished name is case-insensitive
           identity = ::Identity.
             where(provider: provider).
-            where('lower(extern_uid) = ?', uid.mb_chars.downcase.to_s).last
+            iwhere(extern_uid: uid.mb_chars.to_s).last
           identity && identity.user
         end
       end
@@ -31,7 +31,7 @@ module Gitlab
       def find_by_uid_and_provider
         self.class.find_by_uid_and_provider(
-          auth_hash.uid.downcase, auth_hash.provider)
+          auth_hash.uid, auth_hash.provider)
       end
       def find_by_email

lib/gitlab/o_auth/user.rb

@@ -64,7 +64,7 @@ module Gitlab
         # If a corresponding person exists with same uid in a LDAP server,
         # set up a Gitlab user with dual LDAP and Omniauth identities.
-        if user = Gitlab::LDAP::User.find_by_uid_and_provider(ldap_person.dn.downcase, ldap_person.provider)
+        if user = Gitlab::LDAP::User.find_by_uid_and_provider(ldap_person.dn, ldap_person.provider)
           # Case when a LDAP user already exists in Gitlab. Add the Omniauth identity to existing account.
           user.identities.build(extern_uid: auth_hash.uid, provider: auth_hash.provider)
         else

spec/lib/gitlab/ldap/user_spec.rb

@@ -42,6 +42,21 @@ describe Gitlab::LDAP::User, lib: true do
     end
   end
+  describe '.find_by_uid_and_provider' do
+    it 'retrieves the correct user' do
+      special_info = {
+        name: 'John Åström',
+        email: 'john@example.com',
+        nickname: 'jastrom'
+      }
+      special_hash = OmniAuth::AuthHash.new(uid: 'CN=John Åström,CN=Users,DC=Example,DC=com', provider: 'ldapmain', info: special_info)
+      special_chars_user = described_class.new(special_hash)
+      user = special_chars_user.save
+
+      expect(described_class.find_by_uid_and_provider(special_hash.uid, special_hash.provider)).to eq user
+    end
+  end
+
   describe :find_or_create do
     it "finds the user if already existing" do
       create(:omniauth_user, extern_uid: 'my-uid', provider: 'ldapmain')